My problem when doing magic loop for the first time was figuring out where to position the working yarn. They don't show you this in any of the magic loop videos. I was getting an unwanted yarn over when switching needles. I was placing my yarn behind both needles like you would for straight knitting. Your yarn needs to be coming from inside the tube. Every time I switch needles, if my yarn is BETWEEN the front and back needles then I know I'm doing it right.